Flash device breaks the law

Published online 5 November 2012

Habib Maroon

For almost 50 years the number of transistors packed onto a computer chip has doubled every two years, in accordance with Moore's Law. However, as 'top-down' mechanisms, which involve etching the pattern of circuitry from a piece of silicon for writing and storing memory, begin to hit physical limits, an array of various 'bottom-up' techniques are in development.

One idea, pioneered by the laboratory of Sir Fraser Stoddart at Northwestern University, Illinois, relies on self-assembling arrays of mechanically interlocked molecules that can switch between a number of different stable conformations with different electrostatic properties.

In earlier work, the research team had demonstrated that the two different states of these molecules could be harnessed to serve as the 'zeros' and 'ones' of binary code. They have built a memory storage device at a density that Moore's law predicted would only be possible in the year 2020. However, the molecular memory in these prototypes was volatile; the 'one' states would only persist for a few minutes after powering down.

A new study from the group, led by Albert Fahrenbach of Northwestern University, and including Ali Trabolsi of New York University Abu Dhabi, and Youssry Botros of Intel and the National Center for Nanotechnology Research at King Abdulaziz City for Science and Technology (KACST) in Saudi Arabia, has overcome this volatility.

By inserting an additional molecule that serves as an electrostatic barrier into the arrays of molecular switches, the "one" state can be preserved over one hundred times longer. This makes use of interactions between free radicals and provides a mechanism for erasing the stored molecular memory.

"This long-lived 'one' state in combination with an erase mechanism holds promise for the construction of a non-volatile flash memory device based on mechanically interlocked molecular switches," says Fahrenbach.